Hi Ben
In response to your questions:
1. distortion is constant throughout
2. yes
3. yes same distortion, previously they played fine.
Since I posted my question I have found out there is a Focusrite control panel which I found after clicking on 'options' button, the general tab, click on the spanner icon. The Focusrite control panel has three options recording-balanced-mixing the balanced option was selected. It makes no difference to the distortion which option is selected.
Also in the control panel is 'Asio default sample rate' which was set at 44100 and also 'Asio default buffer size' which was set at 256 samples. The control panel also tells me the 'Asio input latency is 16.5ms, the 'Asio output latency' is 16.5ms and the 'Asio total latency' is 32.9ms
thanks
Garry